#include <iostream>
#include <fstream>
using namespace std;

int Ciur(long int number){
	int vector[2000005];
	for(int i = 1; i <= number; i++){
	    vector[i] = 0;
	}
	int nr = 1;
	for (int i = 3; i <= number; i = i + 2){
		if(vector[i] == 0){
			nr++;
		}
		for(int j = i + i + i; j <= number; j = j + i + i){
			vector[j] = 1;
		}
	}
	return nr;
}

int main(){
	ifstream fin("ciur.in");
	ofstream fout("ciur.out");
    long int n, rez;
	fin >> n;
	rez = Ciur(n);
	fout << rez << '\n';
	return 0;
}